Most building structures require the application of protective coatings on exterior areas, such as foundations and roofs, to ensure against the penetration of moisture. It is common practice to apply by means of pressure spray equipment a viscous protective coating, such as asphalt, that is infused with glass fibers. The spray equipment generally is a gun type device having separate sources of asphalt and glass fibers that are simultaneously discharged from a nozzle or barrel end of the device and impinged against the building surface. Spray guns of this type, such as is shown in applicant's prior U.S. Pat. No. 3,185,396, typically require a relatively large source of compressed air such as on the order of 100-125 c.f.m. capacity, for forcefully directing the materials through the gun and onto the building surface. Air compressors of that capacity are relatively expensive and heavy, weighing up to 2000 pounds and more, and usually must be transported to a construction site by truck.